Process for automatically co-ordinating the filling operation of shift elements

ABSTRACT

A process is proposed for automatically coordinating the filling and feeding operation of hydraulically operated and hydraulically or electronically individually commanded shift elements. The filling and feeding operation is divided into a rapid filling phase and a filling equalization phase and has as parameters at least one rapid filling period, one rapid filling pressure, one filling equalization period and one filling equalization pressure. To optimize said parameters two of the four are preset and for the other two, an optimal value is determined for the first parameter to be optimized on the basis of a preset, time-dependent pressure curve in which a pressure increase phase follows the rapid filling phase and equalization phase. To this end, based on an initial value presettable in each case, the first parameter is gradually adjusted until a speed change occurs at or before the start of the pressure increase phase. For the other parameter to be optimized, at the optimal value of the first parameter to be optimized and based on the respective presettable initial value, said parameter is gradually changed until a speed change occurs before or at least approximately simultaneously with the start of the pressure increase phase.

The invention concerns a process for automatically coordinating thefilling and feeding operation of hydraulically or electronicallyindividually controllable shift elements.

BACKGROUND OF THE INVENTION

In order to carry out a gearshift, in automatic transmissions withhydraulically actuated shift elements having a shifting piston moving ina piston space and placed on a disc set, the piston space, which atfirst is more or less filled with air, must be filled with oil beforethe piston is finally placed on the disc set. Said filling and feedingoperation of shift elements is usually divided into a rapid fillingphase and a filling equalization phase. In the rapid filling phase theshift element that operates almost completely or partly idly is filledwith oil, and in the subsequent filling equalization phase the shiftpiston is finally placed on the disc set with less load.

It is generally known from extensive empirical tests that the precisionof said operation, especially with an exactly coordinated feedingpressure, has a very great influence upon the gearshift quality.

In the practice, in transmission coordination, it has repeatedly provenproblematic that the coordination parameters of the filling operation(which are determined by necessary manufacturing tolerances) differ fromone transmission to another. In addition, the coordination parameters ofthe filling operation are also time dependent since the toleranceschange as result of aging and wear through time.

For example, in the rapid filling phase, which fills the piston space(operating idly or partly idly) with oil, the necessary tolerance of theair play determined by the manufacture, that is, the path of the shiftpiston to the discs, together with the manufacturing tolerance, is to beregarded as a variance. If the air play increases, for example, as aconsequence of disc wear, the duration of the filling phase must beextended in order to cover the additional need of oil and to exactlycarry out the feeding operation.

With the former processes known from the practice, it cannot beaccomplished to the extent desired to give a uniform coordination to onetype of transmission.

The necessary filling equalization pressure likewise depends on a seriesof parameters. Thus, when using plate springs, for example, withincreasing rigidity and increasing piston friction, the fillingequalization pressure must be raised in order to place the shift pistonexactly on the discs.

Divergences of pressure regulators also impair shifting quality, wherebya correction of the filling equalization pressure (corresponding to thedivergences of pressure regulators) is required in order to bring theshift pistons, after the filing, to lie on the disc sets with a requiredslight load.

A uniform, single type transmission coordination thus necessarilyresults in gearshifts of reduced quality.

EP 0 435 377 discloses a process for regulating the change from a lowvelocity ratio to a high velocity ratio between the input and outputshafts of an automatic transmission with shift elements, or a couplingand an uncoupling torque transmitting apparatus operated by fluidpressure. In a filling and feeding operation of the hydraulicallyactuated shift elements, the pressure curve is through time adapted tothe transmission conditions by means of an adaptive diagram.

When the engine throttle is substantially closed, the uncoupling, torquetransmitting apparatus is first disengaged by reducing its operatingpressure prior to a change or modification. The coupling, torquetransmitting apparatus is disengaged by applying a coupling instructionpressure for a previously defined filling period. The couplinginstruction pressure, here adjusted to an initial value, is subsequentlyregulated in a close loop regulation period in order to effect aprogressive engagement of the coupling, torque transmitting device. Anincrease in the coupling instruction pressure above a previouslydetermined value during the regulation period, or a moderate filling ofthe coupling transmission apparatus, is detected by the measure of avelocity divergence. According to this detection either a first storedparameter, which relates to the value of the initial couplinginstruction pressure, is adjusted in order to increase the initialcoupling instruction pressure, or a second stored parameter, whichrelates to the length of the filling period, is adjusted in order toextend the filling period.

This process offers the advantage that the gearshift quality is analyzedand required adaptations regarding pressure and time in the fillingperiod are calculated and made the basis of the subsequent gearshifts,whereby their quality is optimized.

However, this known process is disadvantageous in that a learning periodis needed in all driving conditions in order to achieve an optimaloperating condition. Consequently, in a new transmission, after atransmission change, or after transmission repairs, the gearshiftquality is initially impaired when using said known coordinationprocess.

In connection with this, EP 0 435 374 and EPO 0 435 378 are to be citedalso since their adaptation processes also have the disadvantage thatthe parameter optimization acts upon the process only with definitedelay due to the needed learning process.

Therefore, the invention is based on the problem of providing a processof the above mentioned kind in which the separate shift elements foreach transmission are filled from the beginning using optimal parametersin order to ensure an optimal operating quality.

SUMMARY OF THE INVENTION

The process according to the invention offers the advantage that thedecisive parameters for the filling and feeding operation, namely, rapidfilling period, rapid filling pressure, filling equalization period andfilling equalization pressure, can be exactly adjusted individually foreach transmission and in accordance with the tolerance of the individualparts with the startup of the transmission. An immediate optimaloperating condition is thus ensured for each transmission.

According to the process of the invention, the optimization of thefilling operation in transmissions having relatively great tolerances ispossible without problems.

Also, with the principle of the process of the invention, thereadvantageously results a controlled load take-up instead of a sensitiveand costly to regulate load take-up.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the invention result from the sub-claims and fromthe embodiments that follow described with reference to the drawing. Inthe drawing:

FIG. 1 is a diagram of a pressure curve through time with the phases ofa filling;

FIG. 2 is a standard for a pressure regulator current and is atheoretical pressure curve for determining an optimal fillingequalization pressure; and

FIG. 3 is a standard for a pressure regulator current and is atheoretical pressure curve for determining an optimal rapid fillingperiod.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1 to 3, described herebelow is a process for theautomatic coordination of the filling operation of hydraulicallyactuated shift elements wherein the process is exclusively based onparameters like the pressure regulator current periods and differentspeeds already known from the transmission control.

The filling operation of each shift element is described by fourparameters, namely, rapid filling period T₋₋ SF, rapid filling pressurep₋₋ SF, filling equalization period T₋₋ FA and filling equalizationpressure p₋₋ FA.

The filling and feeding operation of hydraulically actuated shiftelements starts first with a rapid filling phase SFP followed by afilling equalization phase FAP. At the end of the filling equalizationphase there follows a pressure increase phase DAP which can bereproduced as a pressure ramp increasing through time, as is to beunderstood from the figures.

Referring to FIG. 1, the generally known phases of a filling arereproduced in the form of a pressure curve dependent on time. With thestart of the rapid filling phase SFP, a rapid filling pressure p₋₋ SF isapplied which remains at least approximately constant during the wholerapid filling period T₋₋ SF. At the end of the rapid filling phase SFP,the pressure curve registers a step and continues with the constantlyproceeding filling equalization pressure p₋₋ FA during the whole fillingequalization phase FAP that follows, which corresponds to the fillingequalization period T₋₋ FA. At the end of the filling equalization phaseFAP there follows a constant pressure increase during the pressureincrease phase DAP. The transition from the filling equalization phaseFAP to the pressure increase phase DAP is characterized by a change ofspeed.

The shift element concerned is thus optimally filled at the end of thefilling equalization phase FAP. If, as a consequence of tolerancesdetermined by the manufacture, the piston space is already filled duringthe rapid filling phase SFP or in an earlier stadium of the fillingequalization phase FAP, or if the filling operation has ended alreadyduring the pressure increase phase DAP, then the shifting operationproceeds jerkily, which is generally felt as a disturbance.

In order to optimize the shifting operation in the sense that thefilling of the shift element terminates with the end of the fillingequalization phase, the rapid filling period T₋₋ SF, the rapid fillingpressure p₋₋ SF, the filling equalization period T₋₋ FA and the fillingequalization pressure p₋₋ FA must be correspondingly optimized. To thisend two of the four parameters mentioned are preset in order todetermine an optimal value for the remaining two parameters p₋₋ FA,opt,T₋₋ FA,opt, p₋₋ SF,opt, T₋₋ SF,opt.

This optimization process for determining an optimal fillingequalization pressure p₋₋ FA,opt and an optimal rapid filling period T₋₋SF,opt is described below.

A condition for carrying out the process is that the rapid fillingpressure p₋₋ SF and the filling equalization period T₋₋ FA be preset.

Besides, it is convenient to know from limiting sample tests lower andupper limiting values for the parameters p₋₋ FA, T₋₋ SF to be optimized.Said limiting values are established empirically in tests with thetransmissions which have maximum tolerances or minimal tolerances andrepresent extreme values having an extremely poor operating quality. Thelower limits of the respective parameters are designated p₋₋ FA,min, T₋₋FA,min, p₋₋ SF,min and T₋₋ SF,min, with the empirically determined upperlimits of the parameters accordingly bearing the designations p₋₋FA,max, T₋₋ FA,max, p₋₋ SF,max and T₋₋ SF,max.

Another condition for carrying out the process is that the shiftelement, the filling parameters of which must be determined, can beindividually controlled hydraulically or electrically. The individualcontrollability of the respective shift element is, therefore, aprerequisite since each shift element has its own tolerances and alsomust be optimally adjusted.

In addition, when said shift element is closed, a measurable speedchange clearly coordinated with the shift element must result. The startof the speed change from the filling equalization phase FAP to thepressure increase phase DAP can be determined by a divergence of thespeed from a mean value, or by the formation of a speed gradient, or bya combination of both. If, for example, a constant engine speed ispreset, this determines a constant system pressure. If a change of speednow follows, a speed change clearly related thereto must appear on theshift element. To this end, the speed and the pressure regulator currentmust always be monitored.

Another added condition is to know by what amount the rapid fillingpressure p₋₋ SF has to be above the filling equalization pressure p₋₋FA. The difference between said pressures is determined with referenceto previous tests and is expressed in the instant embodiment with 1 bar.

Likewise, another condition for carrying out the process has beenestablished with the aid of previous tests, namely, how low the fillingequalization period of the shift element has to be. In the instantembodiment, the filling equalization period T₋₋ FA has been determinedto be 150 ms.

For carrying out the optimization process, the transmission temperatureis first adjusted to a defined level. Thereafter the transmission isbrought to a state such that when the shift element to be adjusted isclosed, a measurable speed change appears. For this purpose other shiftelements, for example, can be closed so that when the shift element tobe adjusted is closed, a gear is introduced, a blocking occurs in thetransmission, or a transmission element is driven at high speed. Byopening the other shift elements, one side of the shift element to beadjusted is brought to a defined output speed. On the other side of theshift element upon which the preset pressure acts, the speed must bemeasurable.

In addition, the engine speed must be raised to the point such that anyinfluence of the system pressure be eliminated when filling the shiftelement. For this purpose, the engine speed must be brought to amagnitude of more than 1,500 U/min, for example.

Referring to FIG. 2, for determining the filling equalization pressurep₋₋ FA, a theoretical pressure curve or pressure regulator current isnow preset having a very short rapid filling phase SFP (substantially 40ms) in order to adjust the hysteresis of the pressure regulator, like ina real shifting operation. The rapid filling pressure p₋₋ SF must beabove the filling equalization pressure p₋₋ FA by 1 bar. For the fillingequalization phase FAP a longer period of time of 3 s duration isassumed. The height of the filling equalization pressure p₋₋ FA to beoptimized is variable.

The pressure ramp (or the pressure increase phase DAP) has a gradient of30 bar/s corresponding to the quickest pressure ramps during shifts.

To determine the optimal filling equalization pressure p₋₋ FA,opt, apressure regulator is now controlled according to the preset pressureregulator current of FIG. 2.

For the filling equalization phase or the current belonging thereto, aninitial value p₋₋ FA,a is first established which is lower than thepreviously empirically determined lower limiting value p₋₋ FA,min. Inthis case, the speed change must take place after the start of thepressure increase phase DAP or pressure regulator current ramp. Ifduring the transition from the filling equalization phase FAP to thepressure increase phase DAP or after the start of the pressure increasephase DAP, no speed change appears, the shift element or the controlthereof is defective.

Therefore, depending on the parameters to be optimized, there is preset,independently of the embodiment described, an initial value p₋₋ FA,a,T₋₋ FA,a, p₋₋ SF,a, T₋₋ SF,a which is conveniently less than therespective empirically determined lower limiting value p₋₋ FA,min,T-FA,min, p₋₋ SF,min, T₋₋ SF,min. This is not an obligatory conditionfor carrying out the optimization process.

Referring again to the optimization of the filling equalization pressurep₋₋ FA of FIG. 2, the initial value p₋₋ FA,a of the filling equalizationpressure is now gradually raised at intervals of 0.1 to 0.2 bar, thespeed change occurring always earlier. At first the speed change stillappears during the pressure increase phase DAP or pressure regulatorcurrent ramp, which means that the adjusted filling equalizationpressure p₋₋ FA is still too low. At a certain filling equalizationpressure p₋₋ FA,opt, the speed change occurs prior to or at the start ofthe pressure increase phase DAP before the pressure regulator currentramp. The filling equalization pressure is the pressure at which for thefirst time the speed change occurs at the start of the pressure increasephase or before.

If the determined optimal filling equalization pressure p₋₋ FA,opt isabove the previously empirically determined upper limited value p₋₋FA,max for the filling equalization pressure p₋₋ FA, then the shiftelement or the control thereof is possibly defective, and in any caseoutside the admissible tolerances.

The same in general applies when a determined optimal parameter p₋₋FA,opt, T₋₋ FA,opt, p₋₋ SF,opt, T₋₋ SF,opt is above the correspondingempirically determined upper limiting value p₋₋ FA,max, T₋₋ FA,max, p₋₋SF,max, or T₋₋ SF,max.

In addition to the preset parameters rapid filling pressure p₋₋ SF,filling equalization period T₋₋ FA, and the determined optimal fillingequalization pressure p₋₋ FA, there must now be determined the optimalrapid filling period T₋₋ SF.

To this end, according to FIG. 3, there is preset a theoretical pressurecurve or pressure regulator current having a rapid filling phase SFP ofvariable duration, a rapid filling pressure p₋₋ SF higher by 1 bar thanthe filling equalization pressure p₋₋ FA, a filling equalization phase(the filling equalization period of which amounts, for example, to T₋₋FA 150 ms), and a pressure increase phase which has a pressure ramp witha gradient of 30 bar/s corresponding to the quickest pressure ramps inshifts.

With the preset parameters p₋₋ SF, T₋₋ FA and the determined optimalfilling equalization pressure p₋₋ FA, opt, there is now first set aninitial value T₋₋ SF which, in turn, is conveniently less than theempirically found lower limiting value T₋₋ SF,min. The speed change nowmust occur after the start of the pressure increase phase DAP, otherwisethe shift element or the control thereof is defective.

Analogous to the above described determination of the optimal fillingequalization pressure p₋₋ FA,opt, the value of the rapid filling periodT₋₋ SF is gradually raised at intervals, the speed change alwaysoccurring earlier. The speed change still appears first during thepressure increase phase, which means that the adjusted rapid fillingperiod T₋₋ SF is still too short. In a specific filling equalizationperiod T₋₋ SF,opt, the speed change occurs simultaneously orapproximately simultaneously with the start of the pressure increasephase DAP and thus constitutes the optimal filling equalization periodfor the shift element.

If the determined optimal rapid filling period T₋₋ SF is above thepriorly empirically determined upper limiting value T₋₋ SF,max, it mustbe assumed that the shift element or the control thereof is possiblydefective, and in any case outside the admissible tolerance.

Analogous to the process described above, it is possible, instead ofoptimizing the rapid filling period T₋₋ SF and the filling equalizationpressure p₋₋ FA, to optimize the rapid filling pressure p₋₋ SF andfilling equalization period T₋₋ FA parameters.

In vehicle inspections this process is conveniently carried out withblocked or stationary output. The process can thus be used both on atransmission inspection bench after manufacture on the belt immediatelyafter the production of the transmission and also in inspections of apassenger car in the workshop.

However, in another embodiment, the process obviously can be carried outwith operating transmission output, for example, while driving.

What is claimed is:
 1. A process for automatically coordinating thefilling and feeding operation of hydraulically operated andhydraulically or electronically individually commanded shift elements,the filling and feeding operation of which takes place according to atime-dependent pressure curve with a rapid filling phase (SFP), afilling equalization phase (FAP) and a pressure increase phase (DAP) andas parameters are used at least a rapid filling time (T₋₋ SF), a rapidfilling pressure (p₋₋ SF), a filling equalization period (T₋₋ FA) and afilling equalization pressure (p₋₋ FA), characterized in that tooptimize the parameters (T₋₋ SF, p₋₋ SF, T₋₋ FA, p₋₋ FA), two parametersare preset and for the other two parameters within a time-dependentpressure curve, an optimal value (p₋₋ FA,opt, T₋₋ FA,opt, p₋₋ SF,opt,T₋₋ SF,opt) of the first parameter to be optimized is determined in amanner such that based on an appropriate presettable initial value (p₋₋FA,a, T₋₋ FA,a, p₋₋ SF,a, T₋₋ SF,a), said value is changed graduallyuntil a speed change occurs with the start of the pressure increasephase (DAP) and the other parameter to be optimized is determined bygradually changing it at the optimal value (p₋₋ FA,opt, T₋₋ FA,opt, p₋₋SF,opt, T₋₋ SF,opt) of the first parameter to be optimized and based onthe appropriate presettable initial value (p₋₋ FA,a, T₋₋ FA,a, p₋₋ SF,a,T₋₋ SF,a) until a speed change occurs at least approximatelysimultaneously with the start of the pressure increase phase DAP.
 2. Theprocess according to claim 1, wherein the presettable initial values(P₋₋ FA,a, T₋₋ FA,a, p₋₋ SF,a, T₋₋ SF,a) are each empirically determinedlimiting values (p₋₋ FA,max, T₋₋ FA,max, p₋₋ SF,max, T₋₋ SF,max).
 3. Theprocess according to claim 1 wherein the shift element or the controlthereof is detected to be defective whena) while increasing a parametervalue for determining the respective optimal value (p₋₋ FA,opt, T₋₋FA,opt, p₋₋ SF,opt, T₋₋ SF,opt) after start of the pressure increasephase (DAP), no speed change occurs and/or b) the determine optimalvalue (p₋₋ FA,opt, T₋₋ FA,opt, p₋₋ SF,opt, T₋₋ SF,opt) is outside arespective empirically determined tolerance range (p₋₋ FA,min, T-FA,min,p₋₋ SF,min, T₋₋ SF,min).
 4. The process according to claim 1 whereinwhen the respective shift element is closed, a measurable speed changeclearly coordinatable with said shift element occurs.
 5. The processaccording to claim 1 wherein the speed change is detected by adivergence of the speed from a mean value and/or by formation of a speedgradient.
 6. The process according to claim 1 wherein said parameters(T₋₋ SF, p₋₋ SF, T₋₋ FA, p₋₋ FA) are optimized at a defined transmissiontemperature.
 7. The process according to claim 1 wherein the preset twoof the four parameters (T₋₋ SF, p₋₋ SF, T₋₋ FA, p₋₋ FA) are empiricallydetermined.
 8. The process according to claim 1 wherein the value ofsaid rapid filling pressure (p₋₋ SF) is selected so as to be above thefilling equalization pressure (p₋₋ FA) by a pre-defined amount.
 9. Theprocess according to claim 1 wherein for optimizing the parameters (T₋₋SF, p₋₋ SF, T₋₋ FA, p₋₋ FA), the speed of an engine interacting with theshift elements is raised until an influence of the system pressure iseliminated.
 10. The process according to claim 1 wherein a transmissionoutput interacting with the shift elements is blocked during theoptimization of the parameters.